At the Fish Collection of the Instituto de Ciencias Biológicas, Escuela Politécnica Nacional, Quito, three species traditionally grouped in the genus Hemiancistrus were identified: H. annectens ...(Regan 1904), H. landoni Eigenmann 1916, and a new specie described here. The new species inhabits exclusively in the Esmeraldas River Basin, Pacific slope, northwestern Ecuador. It is easily recognized by the completely naked abdomen, with rounded, dark spots, and a different color pattern on the dorsal and caudal fins. A comparative analysis of bones related to the opercular mobility, shows important differences between H. annectens, H. landoni, and the new species, suggesting that H. annectens does not belong to the genus Hemiancistrus or the Ancistrini group. According to the characteristics observed in these bones, H. annectens shows greater similarity to those reported in species of the Hypostomini group, supporting its inclusion in this group, but placing it in the genus Hypostomus requires further analysis. On the other hand, the conditions observed on the bones of Hemiancistrus landoni and the new species suggest that both are inside of the Ancistrini group. The new species is placed in the genus Hemiancistrus tentatively, pending future analysis.
Environmental conditions influence ecological processes that shape stream community diversity and abundance. Deforestation has the potential to limit available particulate organic matter and raise ...stream temperatures. The degree to which tropical stream communities are impacted by these changes is likely to differ between systems, but empirical data from tropical regions are lacking. This lack of baseline data hinders conservation policy as well as efforts to better understand biogeographic and anthropogenic impacts on species’ distributions. To fill this knowledge gap, we surveyed 27 sites in six previously unstudied streams across a gradient of deforestation in northwest Ecuador and assessed the degree to which localized deforestation predicted patterns of community composition of fishes. Using general linear mixed models and AICC we found that neither forest fragmentation nor canopy closure was a significant predictor of species richness and found no difference between the species richness of fragmented and continuous sites. However, forest fragmentation was a strong predictor of abundance, occurring in 31 of 31 general linear mixed models, with higher abundance in fragmented forest than in continuous forest. Of 16 species found, eight occurred at five or more sites and one (
Pseudochalceus boehlkei
), numbered 200 out of 627 individuals. NMDS and SIMPER analysis suggested that community composition differed between fragmented and continuous sites
. P. boehlkei
,
Pseudopoecilia fria
, and
Astroblepus
cf.
fissidens
species presented in higher abundances in deforested sites, possibly suggesting a less functionally diverse community. This pattern is consistent with neotropical streams that have experienced partial deforestation but not total degradation of habitat.
Management and conservation of biodiversity requires adequate species inventories. The Yasuní National Park is one of the most diverse regions on Earth and recent studies of terrestrial vertebrates, ...based on genetic evidence, have shown high levels of cryptic and undescribed diversity. Few genetic studies have been carried out in freshwater fishes from western Amazonia. Thus, in contrast with terrestrial vertebrates, their content of cryptic diversity remains unknown. In this study, we carried out genetic and morphological analyses on characin fishes at Yasuní National Park, in eastern Ecuador. Our goal was to identify cryptic diversity among one of the most speciose fish families in the Amazon region. This is the first time that genetic evidence has been used to assess the species content of the Napo Basin, one of the richest regions in vertebrate diversity.
Phylogenetic analyses of partial mitochondrial 16S ribosomal RNA gene (∼600 pb) DNA sequences from 232 specimens of the family Characidae and its closest groups revealed eight candidate new species among 33 species sampled, representing a 24% increase in species number. Analyses of external morphology allowed us to confirm the species status of six of the candidate species.
Our results show high levels of cryptic diversity in Amazonian characins. If this group is representative of other Amazonian fish, our results would imply that the species richness of the Amazonian ichthyofauna is highly underestimated. Molecular methods are a necessary tool to obtain more realistic inventories of Neotropical freshwater fishes.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Small-scale gold mining in Portovelo–Zaruma, Southern Equador, performed by mercury amalgamation and cyanidation, yields 9–10
t of gold/annum, resulting in annual releases of around 0.65
t of ...inorganic mercury and 6000
t of sodium cyanide in the local river system. The release of sediments, cyanide, mercury, and other metals present in the ore such as lead, manganese and arsenic significantly reduces biodiversity downstream the processing plants and enriches metals in bottom sediments and biota. However, methylmercury concentrations in sediments downstream the mining area were recently found to be one order of magnitude lower than upstream or in small tributaries. In this study we investigated cyanide, bacterial activity in water and sediment and mercury methylation potentials in sediments along the Puyango river watershed, measured respectively by in-situ spectrophotometry and incubation with
3H-leucine and
203Hg
2+.
Free cyanide was undetectable (<
1
μg·L
−
1
) upstream mining activities, reached 280
μg·L
−
1
a few km downstream the processing plants area and was still detectable about 100
km downstream. At stations with detectable free cyanide in unfiltered water, 50% of it was dissolved and 50% associated to suspended particles. Bacterial activity and mercury methylation in sediment showed a similar spatial pattern, inverse to the one found for free cyanide in water, i.e. with significant values in pristine upstream sampling points (respectively 6.4 to 22
μgC·mg
wet weight
−
1
·h
−
1
and 1.2 to 19% of total
203Hg·g
dry weight
−
1
·day
−
1
) and undetectable downstream the processing plants, returning to upstream values only in the most distant downstream stations. The data suggest that free cyanide oxidation was slower than would be expected from the high water turbulence, resulting in a long-range inhibition of bacterial activity and hence mercury methylation. The important mercury fluxes resultant from mining activities raise concerns about its biomethylation in coastal areas where many mangrove areas have been converted to shrimp farming.
► Polymetallic and S-rich ore is processed for gold by amalgamation and cyanidation. ► But very low MeHg concentrations are found downstream processing plants. ► Cyanide strongly depressed bacterial activity and mercury methylation along a ~
50
km river stretch. ► Risk for coastal plain: cyanide disappears from ~
110
km on, while Hg does not.
ABSTRACT Parodontidae is a relatively small group of Neotropical characiform fishes consisting of three genera (Apareiodon, Parodon, and Saccodon) with 32 valid species. A vast cytogenetic literature ...is available on Apareiodon and Parodon, but to date, there is no cytogenetic data about Saccodon, a genus that contains only three species with a trans-Andean distribution. In the present study the karyotype of S. wagneri was described, based on both conventional (Giemsa staining, Ag-NOR, C-bands) and molecular (repetitive DNA mapping by fluorescent in situ hybridization) methods. A diploid chromosome number of 2n = 54 was observed in both sexes, and the presence of heteromorphic sex chromosomes of the ZZ/ZW type was detected. The W chromosome has a terminal heterochromatin band that occupies approximately half of the long arm, being this band approximately half the size of the Z chromosome. The FISH assay showed a synteny of the 18S-rDNA and 5S-rDNA genes in the chromosome pair 14, and the absence of interstitial telomeric sites. Our data reinforce the hypothesis of a conservative karyotype structure in Parodontidae and suggest an ancient origin of the sex chromosomes in the fishes of this family.
RESUMO Parodontidae é um grupo relativamente pequeno de peixes caraciformes neotropicais que consiste em três gêneros (Apareiodon, Parodon e Saccodon) com 32 espécies válidas. Uma vasta literatura citogenética está disponível sobre Apareiodon e Parodon, mas até o momento não há dados citogenéticos sobre Saccodon, um gênero que contém apenas três espécies com distribuição transandina. No presente estudo foi descrito o cariótipo de S. wagneri, baseado em métodos convencionais (coloração de Giemsa, Ag-NOR, bandas C) e moleculares (mapeamento de DNA repetitivo por hibridização fluorescente in situ). Um número cromossômico diplóide de 2n = 54 foi observado, e a presença de cromossomos sexuais heteromórficos do tipo ZZ/ZW foi revelada. O cromossomo W possui uma banda terminal heterocromática que ocupa aproximadamente metade do braço longo, sendo esta banda aproximadamente a metade do tamanho do cromossomo Z. O ensaio FISH mostrou uma sintenia dos genes 18S-rDNA e 5S-rDNA no par de cromossomos 14, e a ausência de sítios teloméricos intersticiais. Nossos dados reforçam a hipótese de uma estrutura cariotípica conservadora em Parodontidae e sugerem uma origem ancestral dos cromossomos sexuais nos peixes desta família.
Background Management and conservation of biodiversity requires adequate species inventories. The Yasuni National Park is one of the most diverse regions on Earth and recent studies of terrestrial ...vertebrates, based on genetic evidence, have shown high levels of cryptic and undescribed diversity. Few genetic studies have been carried out in freshwater fishes from western Amazonia. Thus, in contrast with terrestrial vertebrates, their content of cryptic diversity remains unknown. In this study, we carried out genetic and morphological analyses on characin fishes at Yasuni National Park, in eastern Ecuador. Our goal was to identify cryptic diversity among one of the most speciose fish families in the Amazon region. This is the first time that genetic evidence has been used to assess the species content of the Napo Basin, one of the richest regions in vertebrate diversity. Results Phylogenetic analyses of partial mitochondrial 16S ribosomal RNA gene (~600 pb) DNA sequences from 232 specimens of the family Characidae and its closest groups revealed eight candidate new species among 33 species sampled, representing a 24% increase in species number. Analyses of external morphology allowed us to confirm the species status of six of the candidate species. Conclusions Our results show high levels of cryptic diversity in Amazonian characins. If this group is representative of other Amazonian fish, our results would imply that the species richness of the Amazonian ichthyofauna is highly underestimated. Molecular methods are a necessary tool to obtain more realistic inventories of Neotropical freshwater fishes.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A new species of tetraphyllidean eucestode inhabiting Urobatis tumbesensis from inshore waters of southeastern Ecuador shares 3 synapomorphies with Rhinebothroides spp.: apical bothridial suckers ...poorly differentiated from the marginal loculi, internal seminal vesicles, and insertion of the vas deferens dorsally closer to the poral than the aporal end of the cirrus sac. The new species differs from Rhinebothroides spp. by lacking medial bothridial septa and loculi and having symmetrical ovarian arms, and possesses an apparent autapomorphic trait by having the vas deferens tapering to a narrow tube before entering the cirrus sac, extending posteriorly to the posterior end of the cirrus sac where it expands into an external seminal vesicle running ventral to the cirrus sac anteriorly to anterior to the vagina. In Rhinebothroides spp., the vas deferens is expanded into an external seminal vesicle near the insertion into the cirrus sac As the sister group of Rhinebothroides, we propose a new genus to accommodate the new species. Phylogenetic evaluation of phyllobothriids recently assigned to Anthocephalum shows that they represent a paraphyletic assemblage of species of varying degrees of relatedness to Rhinebothroides spp. and the new species. Uncovering the relationships of the new species and the various species assigned to Anthocephalum permitted reevaluation of character transformations used in previous phylogenetic analysis of Rhinebothroides. Transformation series for 3 characters, previously based on functional outgroup comparisons, changed and a new character, length of cirrus sac, was added. The new phylogenetic analysis differs from the previous hypothesis only in placing R. scorzai as the sister species of R. circularisi + R. venezuelae + R. moralarai rather than of R. freitasi + R. glandularis + R. melennanae. The occurrence of the sister species of Rhinebothroides in a Pacific Ocean stingray adds additional support to the hypothesis of Pacific origins of South American freshwater stingrays.
The new Chaetostoma-group genera Andeancistrus and Transancistrus are described based on recently collected material from rivers draining the respective Amazonian and Pacific slopes of the Andes ...Mountains in Ecuador. Andeancistrus is diagnosable from all other members of the Chaetostoma group by having a fully plated snout, lacking cheek odontodes that extend past the opercular flap, and by having eight vs. nine branched dorsal-fin rays. The new species Andeancistrus eschwartzae is also described and diagnosed from its only congener (A. platycephalus) by having a black to dark gray base color of head and body (vs. light gray), irregularly shaped round to vermiculate yellow-gold spots smaller than half naris diameter evenly distributed across head, lateral and dorsal surfaces of the body and fin rays (vs. white to blue uniformly round spots), and by lacking enlarged clusters of odontodes at the posteromedial apex of most lateral body plates (vs. odontode clusters present). Transancistrus contains the species T. aequinoctialis and T. santarosensis, which can together be diagnosed from all other members of the Chaetostoma group except Chaetostoma by lacking plates along the anterior and lateral margins of the snout; they can be diagnosed from Chaetostoma by having a much narrower unplated snout region, approximately as wide as the maximum diameter of the orbit (vs. twice this width). Geographic distributions exclusive of drainages north of Ecuador and strong molecular phylogenetic evidence for a sister relationship between Andeancistrus and Transancistrus support the hypothesis that these genera may have once been contiguously distributed through a low-lying region of northern Peru and been separated via uplift of the Andes Mountains.
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